src/cache.c

   1 /*
   2  * Copyright (C) the libgit2 contributors. All rights reserved.
   3  *
   4  * This file is part of libgit2, distributed under the GNU GPL v2 with
   5  * a Linking Exception. For full terms see the included COPYING file.
   6  */
   7
   8 #include "cache.h"
   9
  10 #include "repository.h"
  11 #include "commit.h"
  12 #include "thread-utils.h"
  13 #include "util.h"
  14 #include "odb.h"
  15 #include "object.h"
  16 #include "git2/oid.h"
  17
  18 bool git_cache__enabled = true;
  19 ssize_t git_cache__max_storage = (256 * 1024 * 1024);
  20 git_atomic_ssize git_cache__current_storage = {0};
  21
  22 static size_t git_cache__max_object_size[8] = {
  23         0,     /* GIT_OBJECT__EXT1 */
  24         4096,  /* GIT_OBJECT_COMMIT */
  25         4096,  /* GIT_OBJECT_TREE */
  26         0,     /* GIT_OBJECT_BLOB */
  27         4096,  /* GIT_OBJECT_TAG */
  28         0,     /* GIT_OBJECT__EXT2 */
  29         0,     /* GIT_OBJECT_OFS_DELTA */
  30         0      /* GIT_OBJECT_REF_DELTA */
  31 };
  32
  33 int git_cache_set_max_object_size(git_object_t type, size_t size)
  34 {
  35         if (type < 0 || (size_t)type >= ARRAY_SIZE(git_cache__max_object_size)) {
  36                 git_error_set(GIT_ERROR_INVALID, "type out of range");
  37                 return -1;
  38         }
  39
  40         git_cache__max_object_size[type] = size;
  41         return 0;
  42 }
  43
  44 void git_cache_dump_stats(git_cache *cache)
  45 {
  46         git_cached_obj *object;
  47
  48         if (git_cache_size(cache) == 0)
  49                 return;
  50
  51         printf("Cache %p: %"PRIuZ" items cached, %"PRIdZ" bytes\n",
  52                 cache, git_cache_size(cache), cache->used_memory);
  53
  54         git_oidmap_foreach_value(cache->map, object, {
  55                 char oid_str[9];
  56                 printf(" %s%c %s (%"PRIuZ")\n",
  57                         git_object_type2string(object->type),
  58                         object->flags == GIT_CACHE_STORE_PARSED ? '*' : ' ',
  59                         git_oid_tostr(oid_str, sizeof(oid_str), &object->oid),
  60                         object->size
  61                 );
  62         });
  63 }
  64
  65 int git_cache_init(git_cache *cache)
  66 {
  67         memset(cache, 0, sizeof(*cache));
  68
  69         if ((git_oidmap_new(&cache->map)) < 0)
  70                 return -1;
  71
  72         if (git_rwlock_init(&cache->lock)) {
  73                 git_error_set(GIT_ERROR_OS, "failed to initialize cache rwlock");
  74                 return -1;
  75         }
  76
  77         return 0;
  78 }
  79
  80 /* called with lock */
  81 static void clear_cache(git_cache *cache)
  82 {
  83         git_cached_obj *evict = NULL;
  84
  85         if (git_cache_size(cache) == 0)
  86                 return;
  87
  88         git_oidmap_foreach_value(cache->map, evict, {
  89                 git_cached_obj_decref(evict);
  90         });
  91
  92         git_oidmap_clear(cache->map);
  93         git_atomic_ssize_add(&git_cache__current_storage, -cache->used_memory);
  94         cache->used_memory = 0;
  95 }
  96
  97 void git_cache_clear(git_cache *cache)
  98 {
  99         if (git_rwlock_wrlock(&cache->lock) < 0)
 100                 return;
 101
 102         clear_cache(cache);
 103
 104         git_rwlock_wrunlock(&cache->lock);
 105 }
 106
 107 void git_cache_dispose(git_cache *cache)
 108 {
 109         git_cache_clear(cache);
 110         git_oidmap_free(cache->map);
 111         git_rwlock_free(&cache->lock);
 112         git__memzero(cache, sizeof(*cache));
 113 }
 114
 115 /* Called with lock */
 116 static void cache_evict_entries(git_cache *cache)
 117 {
 118         size_t evict_count = git_cache_size(cache) / 2048, i;
 119         ssize_t evicted_memory = 0;
 120
 121         if (evict_count < 8)
 122                 evict_count = 8;
 123
 124         /* do not infinite loop if there's not enough entries to evict  */
 125         if (evict_count > git_cache_size(cache)) {
 126                 clear_cache(cache);
 127                 return;
 128         }
 129
 130         i = 0;
 131         while (evict_count > 0) {
 132                 git_cached_obj *evict;
 133                 const git_oid *key;
 134
 135                 if (git_oidmap_iterate((void **) &evict, cache->map, &i, &key) == GIT_ITEROVER)
 136                         break;
 137
 138                 evict_count--;
 139                 evicted_memory += evict->size;
 140                 git_oidmap_delete(cache->map, key);
 141                 git_cached_obj_decref(evict);
 142         }
 143
 144         cache->used_memory -= evicted_memory;
 145         git_atomic_ssize_add(&git_cache__current_storage, -evicted_memory);
 146 }
 147
 148 static bool cache_should_store(git_object_t object_type, size_t object_size)
 149 {
 150         size_t max_size = git_cache__max_object_size[object_type];
 151         return git_cache__enabled && object_size < max_size;
 152 }
 153
 154 static void *cache_get(git_cache *cache, const git_oid *oid, unsigned int flags)
 155 {
 156         git_cached_obj *entry;
 157
 158         if (!git_cache__enabled || git_rwlock_rdlock(&cache->lock) < 0)
 159                 return NULL;
 160
 161         if ((entry = git_oidmap_get(cache->map, oid)) != NULL) {
 162                 if (flags && entry->flags != flags) {
 163                         entry = NULL;
 164                 } else {
 165                         git_cached_obj_incref(entry);
 166                 }
 167         }
 168
 169         git_rwlock_rdunlock(&cache->lock);
 170
 171         return entry;
 172 }
 173
 174 static void *cache_store(git_cache *cache, git_cached_obj *entry)
 175 {
 176         git_cached_obj *stored_entry;
 177
 178         git_cached_obj_incref(entry);
 179
 180         if (!git_cache__enabled && cache->used_memory > 0) {
 181                 git_cache_clear(cache);
 182                 return entry;
 183         }
 184
 185         if (!cache_should_store(entry->type, entry->size))
 186                 return entry;
 187
 188         if (git_rwlock_wrlock(&cache->lock) < 0)
 189                 return entry;
 190
 191         /* soften the load on the cache */
 192         if (git_cache__current_storage.val > git_cache__max_storage)
 193                 cache_evict_entries(cache);
 194
 195         /* not found */
 196         if ((stored_entry = git_oidmap_get(cache->map, &entry->oid)) == NULL) {
 197                 if (git_oidmap_set(cache->map, &entry->oid, entry) == 0) {
 198                         git_cached_obj_incref(entry);
 199                         cache->used_memory += entry->size;
 200                         git_atomic_ssize_add(&git_cache__current_storage, (ssize_t)entry->size);
 201                 }
 202         }
 203         /* found */
 204         else {
 205                 if (stored_entry->flags == entry->flags) {
 206                         git_cached_obj_decref(entry);
 207                         git_cached_obj_incref(stored_entry);
 208                         entry = stored_entry;
 209                 } else if (stored_entry->flags == GIT_CACHE_STORE_RAW &&
 210                            entry->flags == GIT_CACHE_STORE_PARSED) {
 211                         git_cached_obj_decref(stored_entry);
 212                         git_cached_obj_incref(entry);
 213
 214                         git_oidmap_set(cache->map, &entry->oid, entry);
 215                 } else {
 216                         /* NO OP */
 217                 }
 218         }
 219
 220         git_rwlock_wrunlock(&cache->lock);
 221         return entry;
 222 }
 223
 224 void *git_cache_store_raw(git_cache *cache, git_odb_object *entry)
 225 {
 226         entry->cached.flags = GIT_CACHE_STORE_RAW;
 227         return cache_store(cache, (git_cached_obj *)entry);
 228 }
 229
 230 void *git_cache_store_parsed(git_cache *cache, git_object *entry)
 231 {
 232         entry->cached.flags = GIT_CACHE_STORE_PARSED;
 233         return cache_store(cache, (git_cached_obj *)entry);
 234 }
 235
 236 git_odb_object *git_cache_get_raw(git_cache *cache, const git_oid *oid)
 237 {
 238         return cache_get(cache, oid, GIT_CACHE_STORE_RAW);
 239 }
 240
 241 git_object *git_cache_get_parsed(git_cache *cache, const git_oid *oid)
 242 {
 243         return cache_get(cache, oid, GIT_CACHE_STORE_PARSED);
 244 }
 245
 246 void *git_cache_get_any(git_cache *cache, const git_oid *oid)
 247 {
 248         return cache_get(cache, oid, GIT_CACHE_STORE_ANY);
 249 }
 250
 251 void git_cached_obj_decref(void *_obj)
 252 {
 253         git_cached_obj *obj = _obj;
 254
 255         if (git_atomic_dec(&obj->refcount) == 0) {
 256                 switch (obj->flags) {
 257                 case GIT_CACHE_STORE_RAW:
 258                         git_odb_object__free(_obj);
 259                         break;
 260
 261                 case GIT_CACHE_STORE_PARSED:
 262                         git_object__free(_obj);
 263                         break;
 264
 265                 default:
 266                         git__free(_obj);
 267                         break;
 268                 }
 269         }
 270 }